Telephone system



Sept. 16,1941. H. DREYER ETAL 2,255,765

TELEPHONE SYSTEM Filed March 1, 1959 INVENTORSI HANS DREYER BY IEGFRIED KRAATZ ATTORNEY.

I Patented Sept. 16, 1941 TELEPHONE SYSTEM Hans Dreyer, Falkensee, near Berlin, and Siegfried Kraatz, Berlin-Waidmannslust, Germany, assignors to Fides Gesellschaft fiir die Verwaitung und Verwertung von gewerblichen Sclmtzrechten m. b. 11., Berlin, Germany Application March 1, 1939, Serial No. 259,276

In Germany March 11, 1938 'IClaims.

The invention relates to selectors for remote signalling installations and in particular to test circuits for these. The seizing of a selector is manner and on a free line leading to a subsequent selector for example the group selector known in general to be accompanied by an electric guarding for the most part in order that the testing devices of further access means to the seized selector may be prevented from hunting for connecting devices on the switching through of the connection. This is in .general carried out by means of a switching over on the testing device of .the previously arranged connecting device which lowers the testing potential.

In systems with forwardly directed release in known arrangements the disappearance of this locking potential is at the same time the criterion for the release of the seized selector. Up to the complete setting back of the switching of the releasing selector to its normal position, the guarding against seizing by other connecting devices is therefore removed which can lead to disturbances in the ordinary setting up of connection in automatic telephone systems.

The object of the invention is to prevent such disturbances which is done in a particularly simple and eiiective manner so that switch means operated by the selector leaving its normal position reduce the test .potential for. the preceding connecting device by dividing the potential or switching over on to a divided potential until the complete setting back of the selector in its home positions.

In the drawing 3 embodiments of the inventions are shown.

Figure 1 shows an arrangementin which the potential dividing is carried out by the series dividing of several resistances.

In Figure 2 a similar arrangement is shown in which however for potential dividing windings of the seizing relay itself are used.

In the arrangement according to Figure 3 the test potential is reduced after the seizing of the selector by switching over the testing selector on to a dividing point of the operating battery.

The arrangement shown in Figure 1 is first described in brief. Two group selectors are indicated by GWI and GW! whose known setting and control circuit are not shown on account of their simplicity. Only the test circuit forming the subject of the invention is described in detail. On'the seizing of the group selector GWI on the left relay A is energized over its windings I and II by the feeding current of the calling subscriber's set. it connects a slow relay V. After the group selector on the required By closing, its contact la the setting of bank in known GW2 the following test circuit is completed: earth, contact iv of the selector GWI, windings I and II of the test relay P, lower wiper of GWI, seizing relay C of the group selector GW2, resistance W2, battery, earth. On its operation relay P closes its contacts 3p, 4p, in. By means of the first-mentioned contact its high resistance winding I is short-circuited and thus the guarding of the test contact of the seized selector GW2 is carried out. By the closing of the contacts in and in the talking conductors are switched through to those of the selector GW2. As soon as this has left its normal position on the sending out of further impulse trains in a manner not shown here the vertical oiI-normal contact I: is closed and thus the resistance W1! is connected parallel to the relay 0 and to the winding II of the relay P in the previous group selector GWI. The dividing of the potential carried out in this, manner reduces the guarding potential on the test contact 9 of the selector GW2.

when now the conversation is. over and the calling subscriber hangs up his receiver relay A restores and a short while afterwards the relay V. By the opening of the contact 212 the test circuit is interrupted so that the relays P and C restore. The relay-C eil'ects the release of the group selector GW! in known manner. Since now the contact 6k remains closed until the final setting back of the selector GWZ to its home position there is only a small potential on the test contact of this selector so that the test relay of another group selector testing on this contact during this period does not receive sufficient current to operate. In this manner a positive guarding of the selector GW2 is maintained until this is finally set back in its home position.

In Figure 2 showing the further embodiment only the test circuit is indicated. On the testing of the wiper on the next selector the following test circuit is completed: earth, contact 2v, windings I and II of relay P, test wiper of the first group selector, winding I of relay C, battery, earth. In this circuit relays P and O operate of which the relay P short-circuits its high resistance winding I by closing its contact In and relay 0 prepares the setting of the second group selecton, As soon as this has left its normal position the contact I: is closed and thus the winding 11 of relay P. The winding II of relay C is so connected that the magnetic field produced by it in the common relay core is in the P the current flowing through the winding II of relay C is so small that the magnetic'fleld produced by it-only partially removes the effect of the winding I of relay C so that the armature of the relay C still remains attracted. When 1 now at the termination of the connection the 10 relay P restores and also the relay C since its contact 20021 the previous selector is opened the winding II now carries an essentially stronger current. During the release movement of the second group selector the contact 610 remains closed however so that the test potential controlling contact 9 is not suillclent to cause the operation of the relay P of another subsequently 1 j testing first group selector.

selector has reached the normal position the contact 6k is opened and hence the normal testing potential is connected over the winding I of relay If the second group C to the test contact 9.

In Figure 3 only the test circuit is shown. soon as the wiper has reached the test contact i 9 to which the seizing relay C is connected the following test circuit is completed, earth, contact 212, windings I and II of relay P, test wiper of the first group selector, winding of relay C, var,-

. tical oif normal contact 1k in its normal position, battery B, earth. The relay P by means of its contact 3p short-circuits again its high resistance winding I and thereby guards the second I group selector seized against further seizing by.

other first group selectors. When the second group selector now leaves its normal position its vertical oil-normal contact is operated from the position 870 and thus the test circuit is connected i only to'part of the potential of the battery B. i 5 When at the termination of the connection the 1 contact 212 in the first group'selector is opened the relays P and C restore. the release of the second group selector. i til the'termination oi the release movement of l the selector the contact 8k remains closed and hence the test potential for a i'urtlier testing 45 first group selector is maintained insufilcient to 1 energize the corresponding test relay. Only when the second group selector has reached its normal position is the contact 'llc again closed and hence 1 normal test potential applied. 5

What is claimed is: v

1. In a switching system, a selective switch having a normal position and an oil-normal position, means for seizing said switch and moving it to its oilnormal position, a test terminal for the switch, a source of potential always connected to' 'said terminal, and means oper'atedwhen the switch is moved oil normalto reduce theeflective potential connected to said terminal and ,0

maintain such reduced potential thereon-until the switch again reaches its normal position.

2. In a switching system, a .selective switch having a normal position and an off-normal position, means for seizing said switch and moving it 'from'said normal position to said oil-normal position, a test terminal for the switch, a source of current connected to said terminal and normally maintaining same at a certainpotential, and means operated when the switch is moved off normal to reduce the potential of said terminal to: a point above zero and to maintain said reduced potential thereon until the'switch'is restored to its normal position. v

3. In aswitching system, a selective switch The relay C efiects 1 opposite direction to the field produced by the windingI. In view or the parallel connection 1 or the low resistance winding II of the relay having a normal position and an oil-normal position, a test terminal for the switch, a source of direct current connected to said terminal and maintaining said terminal at a certain potential when the switch is idle and at normal, means for seizing said switch and moving it to said 011- normal position, means operated when the switch is moved off normal to alter the potential of said terminal and maintain the altered potential thereon until the switch is restored to its normal position, said altered potential being of the same polarity. as said certain potential but of a different value. p

4. In a switching system, a selective switch having a normal position and an oil-normal position, a test terminal 'for said switch, a source of direct current, a permanent connection from said source to said terminal, said source maintaining said terminal at a certain potential over said connection when said switch is idle and at normal, means for seizing said switch and moving it tosaid off-normal position, and means operated-when the switch is moved ofi normal to complete another connection to said terminal to reduce the potential thereof, said last means effective to maintain said reduced potential on said terminal until the switch again reaches its normal position.

5. In an automatic switch having a normal position and an off-normal position, a source of current, said source having two oppositely poled output terminals, two resistors, a test terminal always connected to one of said output terminals through one of said resistors, and means oper-' ated only when the switch is in a particular one of said positions to also connect said'test terminal to the other one of said output terminals through the other of said resistors, whereby the potential of said test terminal varies in dependence upon whether said switch is in its normal position or in its oil-normal position.

. 6. In a switching system, a selective switch having a normal position and an oil-normal position, twosources of current, a test terminal for i said switch connected to one of said sources when said switch is in one of said positions and main-' tained at a certain potential by said one source alone, and means operated when the switch is in the other 01 said positions to connect said terminal to both of said sources in series, said sources in series maintaining said terminal at a diflerent potential while the switch is in said other position.

7. In a system employing automatic switching equipment, a selecting device having a normal position and adaptedto be moved there'- from, other selecting devices having access to said, first device, a test conductor in said'first device, a source of direct current connected to said conductor and maintaining same at a certain potential when said first device is idle and at normal, means in one of said other devices for testing said conductor and seizing 'said first device, and means efiective if said first device is then moved from its normal position for altering the potentiaLof said conductor and preventing its restoration to said certain potential until 

